SOMETIME AFTER MIDNIGHT ON APRIL 8, 1998, A MAN AND A WOMAN near Birmingham, Ala., woke up to hear the freight-train roar of a powerful tornado approaching their mobile home. With only moments to react, the couple placed their three-year-old daughter in the best shelter they could think of: their clothes dryer. It was to be their last decision as parents.

The industry does not like the popular phrase “mobile home” —it reserves that term for units built before the federal government began regulating its product. Until 1976, house trailers were not subject to any building code. Since 1976, the industry has been covered by a federal rule known as the HUD Code, and in 1994, in the aftermath of Hurricane Andrew, the HUD Code was toughened for coastal high-wind zones. Manufacturers call units built after 1976 “manufactured housing” or “HUD-Code homes,” pointing to the national rules as an assurance of quality.

But the 1994 code revision (which an industry association, citing cost factors, tried to block in federal court) does not apply to units in the nation's midsection. And, call it what you want, a lightly framed, narrow box, braced mainly with drywall or thin paneling and resting on stacks of cement blocks, is no place to hide from nature's most violent wind-storm. News accounts of tornadoes routinely mention death and destruction at mobile-home neighborhoods—commonly enough to spawn popular rumors that “trailer parks” somehow actually attract tornadoes. Engineer Tim Reinhold, now vice president for engineering at the insurance industry–sponsored Institute for Business and Home Safety, even recalls an official inquiry from a congressman's office to the government agency where he once worked: The congressman wanted to know whether tornadoes could really seek out mobile-home parks.

“Because it came from a congressman,” Reinhold remembers, “we actually had to treat that as a serious question.” But the truth is more ordinary, he says. Reinhold explains that elevated rates of death and injury in mobile homes stem from the way the structures are built and set: “By any objective standard, mobile homes, particularly the ones that are built in the middle of the country where tornadoes are likely to occur, don't have the kind of strength that you get with a site-built home.”

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SURVIVAL OF THE FITTEST: Above, a conventional house in Newburgh, Ind., had its roof ripped off by the  same storm that killed 18 residents of the Eastbrook Mobile Home Park. At  right, student volunteers salvage an appliance from a destroyed Newburgh  house. Strong tornadoes can destroy even well-constructed site-built homes; however, the  survival of even one interior room (or “core element”) can  spell the difference between life and death.
SURVIVAL OF THE FITTEST: Above, a conventional house in Newburgh, Ind., had its roof ripped off by the same storm that killed 18 residents of the Eastbrook Mobile Home Park. At right, student volunteers salvage an appliance from a destroyed Newburgh house. Strong tornadoes can destroy even well-constructed site-built homes; however, the survival of even one interior room (or “core element”) can spell the difference between life and death.
TRAIL OF TRAGEDY: Shown here is a portion of the storm track from the September 2005 Evansville  tornado. Luck plays a major role in tornado events, as homes in the storm's  narrow track may be pulverized while buildings a hundred feet away escape  damage. But strong in-flow winds can also suck poorly anchored manufactured  units off their pads and into the vortex.
TRAIL OF TRAGEDY: Shown here is a portion of the storm track from the September 2005 Evansville tornado. Luck plays a major role in tornado events, as homes in the storm's narrow track may be pulverized while buildings a hundred feet away escape damage. But strong in-flow winds can also suck poorly anchored manufactured units off their pads and into the vortex.
BREAKING LOOSE: Ground anchors failed in multiple ways in the September 2005 Evansville storm. Straps  may pull through the anchor ratchet (above), or anchor bolts may  shear off, leaving the ratchet attached to the strap (next photo). At bottom right, an  earth-auger anchor has been bent and twisted by off-center forces. Earth  anchors in particular tend to take up strain at varying rates due to  variations in soil strength or anchor depth, forcing some anchors to handle  loads beyond their rated capacity.
BREAKING LOOSE: Ground anchors failed in multiple ways in the September 2005 Evansville storm. Straps may pull through the anchor ratchet (above), or anchor bolts may shear off, leaving the ratchet attached to the strap (next photo). At bottom right, an earth-auger anchor has been bent and twisted by off-center forces. Earth anchors in particular tend to take up strain at varying rates due to variations in soil strength or anchor depth, forcing some anchors to handle loads beyond their rated capacity.
HOW TIE-DOWNS FAIL: In a typical installation (above), the unit's chassis is set on stacked masonry  block with wood leveling shims and tied down with steel straps wrapped  around the chassis I-beams. Over-the-top straps to resist overturning are  often provided, but are only required to be actually used in Zones II and III  near the coast, not in Zone I inland. In this photo, the over-the-top strap  is still rolled up in its “factory roll.” Above right, a tie  strap that snapped in the Evansville storm lies on the concrete pad. Straps  commonly tear at the beam from metal fatigue and eccentric loading (next photo).
HOW TIE-DOWNS FAIL: In a typical installation (above), the unit's chassis is set on stacked masonry block with wood leveling shims and tied down with steel straps wrapped around the chassis I-beams. Over-the-top straps to resist overturning are often provided, but are only required to be actually used in Zones II and III near the coast, not in Zone I inland. In this photo, the over-the-top strap is still rolled up in its “factory roll.” Above right, a tie strap that snapped in the Evansville storm lies on the concrete pad. Straps commonly tear at the beam from metal fatigue and eccentric loading (next photo).
WRENCHED APART: When anchors are stressed unevenly, failure of one tie-down may transfer its  load to the next, and a domino effect can quickly “unzip” the  entire tie-down system and subject the unit to bending and twisting forces  not considered in the unit's structural design. Concentrated forces may rip  the unit off its chassis, pull the chassis from its anchors, or both. The  mangled chassis above has lost its trailer; the chassis at right lies in a  pile of debris.
WRENCHED APART: When anchors are stressed unevenly, failure of one tie-down may transfer its load to the next, and a domino effect can quickly “unzip” the entire tie-down system and subject the unit to bending and twisting forces not considered in the unit's structural design. Concentrated forces may rip the unit off its chassis, pull the chassis from its anchors, or both. The mangled chassis above has lost its trailer; the chassis at right lies in a pile of debris.
ENVELOPE CHOICES: Sheathing makes a difference in the storm performance of structures. Here, foamboard  sheathing (photo #13) and asphalted particleboard sheathing (previous photo) have  been stripped off two units at the Eastbrook Mobile Home Park, along  with the vinyl siding. In the next photo, a unit that was blown off its foundation  still retains some shape because of its structural panel sheathing.
ENVELOPE CHOICES: Sheathing makes a difference in the storm performance of structures. Here, foamboard sheathing (photo #13) and asphalted particleboard sheathing (previous photo) have been stripped off two units at the Eastbrook Mobile Home Park, along with the vinyl siding. In the next photo, a unit that was blown off its foundation still retains some shape because of its structural panel sheathing.
NEVER CONNECTED: A system is only as strong as its weakest link. At left, block piers sit where  a unit had been placed with no tie-down anchors, sitting unsecured on the  piers. Scattered debris in the background is all that remains of the unit—while  a better-secured nearby unit shows no damage.
NEVER CONNECTED: A system is only as strong as its weakest link. At left, block piers sit where a unit had been placed with no tie-down anchors, sitting unsecured on the piers. Scattered debris in the background is all that remains of the unit—while a better-secured nearby unit shows no damage.
DEGREES OF DAMAGE: Here, photos show several degrees of damage to mobile homes. Tornado wind speed  is estimated from the observed damage. Although newer units may perform  better than older ones, mobile homes in general tend to suffer worse damage  than site-built houses in small tornadoes. Total destruction of a mobile  home might only indicate a tornado of strength F2 or F3, while total destruction  of a site-built house might indicate a tornado of strength F4 or F5.
DEGREES OF DAMAGE: Here, photos show several degrees of damage to mobile homes. Tornado wind speed is estimated from the observed damage. Although newer units may perform better than older ones, mobile homes in general tend to suffer worse damage than site-built houses in small tornadoes. Total destruction of a mobile home might only indicate a tornado of strength F2 or F3, while total destruction of a site-built house might indicate a tornado of strength F4 or F5.

Government scientists at the National Weather Service keep track of tornado deaths, noting where and how they occur. The numbers they see prompt them to include specific advice in their tornado warnings: If you're in a mobile home, get out and seek better shelter. Those who stay in their mobile homes, in the words of one Red Cross official, risk “becoming a part of the debris field along with your mobile home.”

But better shelter is not always close at hand, and the advice may feel counterintuitive to citizens—who wants to venture out of a dry trailer in the middle of the night into pelting rain, hail, lightning, and wind? And tornadoes really are rare and concentrated events. Even in a tornado watch, the odds between the chance of total destruction if you stay put and the certainty of being exposed to ordinary rough weather if you go outside to hunt for better protection often fall short of convincing people to leave their homes. For those of us who have never experienced it, it is hard to imagine the overwhelming violence of a killer tornado—and until the storm actually hits, a manufactured house may still feel like adequate refuge.

The Alabama parents who put their pre-school daughter into a clothes dryer that spring night in 1998 made a desperate, last-minute choice that saved the little girl's life. After the storm, rescuers found the child still in the dryer and unhurt, 250 yards from where her home had stood. Choosing to remain in the trailer at all, however, resulted in disaster for the parents. The clothes dryer proved better shelter than the home itself, and the couple received fatal injuries as their mobile home rolled 100 yards and came to rest against another building. Had the unit been equipped with an in-ground shelter, the whole family could have survived, and the girl would likely still have her parents today.

RISKS IN PERSPECTIVE In a world full of risks, every safety choice is a roll of the dice; tornado hazards bring up their own calculation of the odds. And the fact is that violent tornadoes are quite rare compared to the everyday risks of life. Some 1,500 tornadoes are reported each year in the U.S. It sounds like a lot, but America's a big country—so even for Tornado Alley states, such as Oklahoma, the odds are a thousand to one against seeing even a weak tornado in a given square mile in a given year.

Moreover, most tornadoes are weak. The violent tornadoes that cause most of the death and destruction are only about 5 percent of the total. An average square mile in the U.S. heartland could easily go 50,000 years without experiencing a real killer tornado, and that's for the whole square mile—the chances the storm would hit one particular building are even lower. In a typical year, tornadoes might kill 50 to 80 Americans. That puts twisters in the same ballpark as snakebites (about 15 deaths per year) and lightning strikes (about 85 deaths per year). Tornado fatalities are far less commonplace than fatal auto crashes, gun deaths, or even deaths caused by falling down stairs. (As of mid-September, tornadoes have killed 54 Americans in 2006, according to the National Weather Service; the fraction involving mobile homes is not yet published.)

But when tornadoes do hit, your choice of housing sharply affects your risk of death. Meteorologists Harold Brooks and Chuck Doswell, from the National Oceanographic and Atmospheric Administration, have analyzed the historic data on tornado fatalities and found that recent numbers reveal a steep decline. In a paper published in 2002, they report: “The number of deaths per year caused by tornadoes has generally been much less in the last quarter of the 20th century than it was previously. In particular, the number of deaths in the ‘big years' has dropped dramatically.” Brooks and Doswell go on to explain that between 1875 and 1974, there were 54 years wherein at least 100 tornado deaths occurred per year. However, the statistics drastically improve between 1975 and 2000, wherein only two years (1984 and 1998) contained as many as 100 tornado deaths.

Learn more about markets featured in this article: Evansville, IN.